THE BONES OF THE SKULL. I51 
nasal cavity. It is united with the cartilaginous nasal septum and 
also with the presphenoid. It forms the terminal member of the 
chain of bones lying in the basicranial axis. 
The ethmoidal labyrinth (labyrinthus ethmoidalis) occupies 
for the most part the posterior portion of the nasal fossa, but the 
nasoturbinal extends forward to its anterior end, and is attached 
for the greater part of its length to the internal surface of the nasal 
bone. It is broadest in its middle portion, where it projects into 
the space left between the ethmoturbinal proper and the maxillo- 
turbinal, and contains at this point a pouch-like cavity, termed the 
mMmarsupium nasale. The whole structure is comparable to one 
of the folds of the ethmoturbinal proper; but it is frequently seen 
to be divided into anterior and posterior parts by a thin vertical 
line of cartilage, the anterior division being probably allied to the 
maxilloturbinal. Its middle, ventral, portion bears a_ stout, 
backwardly-directed uncinate process (processus uncinatus), 
which is applied to the medial surface of the maxilla. 
The ethmoturbinal proper consists, as described above, of 
several shorter scrolls, decreasing in length from above downward. 
Like the posterior part of the nasoturbinal, they are attached 
directly to the cribriform plate, the perforations of which may be 
seen in the divided skull opening into the ethmoidal scrolls 
ot spaces contained by them. They are roughly comparable to the 
superior and middle turbinated bones of the human skull, but in 
the rabbit, as in most mammals, the ethmoturbinal surfaces are 
relatively much more extensive than in man. 
In the typical mammalian skull the ethmoid bone is exposed 
to the orbit, where it forms a thin plate of bone, the lamina 
papyracea. In the rabbit, however, the space usually occupied 
by the lamina papyracea is partly filled by the lacrimal bone, the 
ethmoidal process of the orbitosphenoid and the sphenoorbital 
process of the maxilla. 
11. THE INFERIOR TURBINATED BONE. 
The inferior turbinated bone (concha nasalis inferior), or 
maxilloturbinal, is a finely ridged structure, situated anteriorly 
in the nasal fossa, and supported by the maxilla and premaxilla. 
